Prince William and Kate Middleton waited until George was 7 to tell him he would be king

Prince George was told on his 7th birthday that he will one day be king, a new book claims.

According to the book, it was Prince William who made the decision to wait until George turned 7 to tell him about his future and explain his royal bloodline to his son.

Author Robert Lacey says the Duke of Cambridge was the one who chose for his son to find out about it later in life than what is normally done, breaking the news to him gradually over time.

Prince William and Prince George. Photo / Getty Images

William's goal was to give his son a normal life for as long as possible, Lacey says in his book Battle of Brothers.

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"From George's earliest days, William made no secret of his wish to spare his firstborn the casual initiation – or non-initiation – that he felt he had suffered as a child," Lacey claims.

According to the Daily Mirror, while it is not known exactly when the conversation with Prince George happened, it is believed to have taken place around his 7th birthday, in July last year.

The author says George did not know why he was pulled away from a Christmas party to pose alongside his father, grandfather Prince Charles and great-grandmother the Queen, for the "Four Monarchs" photo taken in 2019.

"William's aim as a father, the prince stressed, was to give his son a 'normal family upbringing' enabling the monarchy to 'stay relevant and keep up with modern times'," Lacey writes.